JPH07102407B2 - Press forming method for cylindrical work - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-forming a cylindrical work, and particularly to a corner formed by a bottom and a body of a work that has been previously drawn into a cylindrical shape (cup-shaped) with a bottom. The present invention relates to a molding method for finishing an edge portion as sharply as possible.

2. Description of the Related Art For example, in a cup-shaped work 1 as shown in FIG. 2, a peripheral groove 4 for mounting a snap ring or the like is formed on a portion of the outer peripheral surface of the body portion 2 close to the outer bottom surface 3a. There is.

As a processing procedure of the work 1 having such a circumferential groove 4, a predetermined blank material is first drawn into a cup shape as shown in FIG. 3, and at this time, the bottom portion 3 is formed. Bulge 5 protruding outward at the peripheral edge of the
Is formed.

Then, in the restrike process following the drawing process, as shown in FIG.
Then, the work 1 is pressed and restrained by the lower die punch 9, and the work 1 is finished into a predetermined size and shape by squeezing with the die 7 while squeezing the bulging portion 5 until the entire bottom portion 3 becomes flat.

After this, as shown in FIG. 5, a surplus portion 10 formed on the bottom portion 3
While removing (the portion hatched in FIG. 5 by cross-hatching) by machining such as end face cutting, the body portion 2
Similarly, a groove is formed by machining (a portion to be cut and removed by the groove is shown by cross hatching S) to form the circumferential groove 4, so that the final product shape shown in FIG. 2 is obtained.

According to the conventional method, at the stage after the re-strike process, the outer corner edge portion 11 formed by the body portion 2 and the bottom portion 3 is so-called "dare" as a peculiarity of plastic working. A phenomenon occurs, and the radius of curvature of the corner edge portion 11 becomes larger than the theoretical value. That is, in theory, the radius of curvature of the outer corner edge portion 11 should be the sum of the radius of curvature of the inner corner edge portion 12 and the plate thickness. Grows larger.

As a result, as shown in FIG. 5, when the distance from the outer bottom surface 3a, which is the final product shape of the work 1, to the circumferential groove 4 is small, the curved portion of the corner edge portion 11 reaches the position where the circumferential groove 4 should be formed. Therefore, even if the groove is processed, it is impossible to form the peripheral groove 4 having a regular size and shape.

The present invention has been made in view of the above problems,
It is an object of the invention to provide a molding method capable of significantly reducing the radius of curvature of the outer corner edge portion without increasing the number of steps.

Means for Solving the Problems The present invention is to press-constrain a work having a bulging portion whose peripheral edge portion bulges outward toward the outside by being press-formed in advance in a cylindrical shape having a bottom, and to press and restrain the work with the entire bottom portion. Is a method of forming the outer corner edge part formed by the bottom part and the body part into an acute angle shape by crushing the bulging part until it becomes a flat shape, and the molding surface of one mold pressed against the outer bottom surface of the bottom part. A printing pressure convex portion is formed in a portion corresponding to the bulging portion,
In the process of forming the entire bottom portion into a flat shape, the printing pressure convex portion is used for printing until the peripheral edge portion of the bottom portion is thinner than other portions of the bottom portion.

Operation According to the method of the present invention, when the peripheral edge of the bottom is pressed by the printing convex portion formed on one of the molds, the raw material meat of the pressed portion moves, and a part of it moves to the body and the outer bottom surface. Since it is replenished to the outer corner edge portion formed by, the radius of curvature of the outer corner edge portion becomes smaller.

Embodiments FIGS. 1A and 1B are views showing an embodiment of the present invention.
In the press die used in the wrist-like process, a portion of the molding surface 14a of the pad 14 that corresponds to the peripheral edge of the bottom portion 3 of the work 1, that is, a portion that pressurizes and restrains the bulging portion 5 of FIG. The printing pressure convex portion 15 is formed in advance. The height of the printing pressure convex portion 15 is set to about a fraction of the plate thickness of the bottom portion 3.

Then, as shown in FIG. 3, the work 1 that has been previously drawn into a cup shape is pressed and restrained by the pad 14 and the punch 9 of FIG. 1A, and the flat bottom portion 3 is crushed while the bulging portion 5 is crushed.
In the process of molding, the peripheral portion of the bottom portion 3 is printed with the printing pressure convex portion 15.

Due to this printing operation, the material meat of the pressed portion moves, and the material meat moves not only to the central portion of the bottom portion 3 but also to the space outside the corner edge portion 11 not constrained by the pad 14 at all. As a result, the raw material meat is replenished to the outside of the corner edge portion 11 to prevent the occurrence of "drip" as in the conventional case, and the radius of curvature of the corner edge portion 11 is also reduced, so that the outer corner edge portion The radius of curvature of 11 can be made smaller than the radius of curvature of the inner corner edge portion 12 to form a sharp edge shape.

The work 1 that has undergone such restrike processing is subjected to machining as in the conventional case, and as shown in FIG. 1 (B), a surplus portion 17 including a step 16 generated by the preceding printing pressure (cross hatching is performed). (The portion marked) is removed by end face cutting, while the peripheral groove 4 is formed on the outer peripheral surface of the body portion 2 by grooving (the portion to be cut and removed by grooving is indicated by cross hatching S).
To form.

At this time, even if the position of the circumferential groove 4 is close to the outer bottom surface 3a, the outer corner edge portion 11 formed by the body portion 2 and the outer bottom surface 3a has a sharp edge shape as described above. The curved portion of the corner edge portion 11 does not extend to the circumferential groove 4, and the straight portion 18 having a length l is secured between the corner edge portion 11 and the circumferential groove 4 to ensure that the circumferential groove 4 has a regular shape.
Is formed.

EFFECTS OF THE INVENTION As described above, according to the present invention, the printing pressure convex portion is formed in the portion corresponding to the bulging portion of the bottom peripheral edge of the molding surface of one mold that is pressed against the outer bottom surface of the work bottom portion, In the process of molding the entire bottom into a flat shape, the printing pressure is applied by the printing projection until the peripheral edge of the bottom becomes thinner than the other parts of the bottom. The material meat of the part moves and is replenished to the outer corner edge part formed by the bottom part and the body part, so that the conventional "drip" is prevented and the radius of curvature of the corner edge part is remarkably reduced. Therefore, the corner edge portion can be formed into a sharp edge shape.

Therefore, for example, even when the circumferential groove is formed at a position close to the corner edge portion in the body portion, the size and shape accuracy of the circumferential groove are not deteriorated.

[Brief description of drawings]

FIG. 1 (A) is an explanatory view of a re-strike process showing an embodiment of the present invention, and FIG. 1 (B) is an enlarged view of part a of FIG.
FIG. 2 is a cross-sectional view showing an example of a work in which a circumferential groove is formed,
FIG. 3 is a cross-sectional view showing the shape of the work before restriking and after drawing, FIG. 4 is an explanatory view of a conventional restriking process, and FIG. 5 is an enlarged view of part b of FIG. 1 ... Workpiece, 2 ... Body, 3 ... Bottom, 3a ... Outer bottom surface, 4 ... Circumferential groove, 5 ... Swelling section, 6 ... Upper mold, 9 ... Punch as lower mold, 11 …… Outer corner edge, 14
a: Molding surface, 15: Printing pressure protrusion.

Claims (1)

[Claims] 1. A work having a bulging portion in which a peripheral portion of the bottom portion is bulged in advance in a cylindrical shape having a bottom and is press-restrained by an upper and lower dies until the entire bottom portion has a flat shape. A method for forming an outer corner edge portion formed by a bottom portion and a body portion into an acute angle shape by crushing the bulging portion, wherein the bulging portion of the molding surface of one of the molds pressed against the outer bottom surface of the bottom portion. In the process of forming a printing pressure convex portion on a portion corresponding to the above, and molding the entire bottom portion into a flat shape, the printing pressure convex portion is used until the peripheral edge portion of the bottom portion is thinner than other portions of the bottom portion. A method for press-forming a cylindrical work, comprising: